3d ultrasound imaging system

ABSTRACT

The present invention relates to an ultrasound imaging system comprising:
         an image processor configured to receive at least one set of volume data resulting from a three-dimensional ultrasound scan of a body and to provide corresponding display data,   an anatomy detector configured to detect a position and orientation of an anatomical object of interest within the at least one set of volume data,   a slice generator for generating a plurality of two-dimensional slices from the at least one set of volume data, wherein said slice generator is configured to define respective slice locations based on the results of the anatomy detector for the anatomical object of interest so as to obtain a set of two-dimensional standard views of the anatomical object of interest, wherein the slice generator is further configured to define for each two-dimensional standard view which anatomical features of the anatomical object of interest are expected to be contained, and   an evaluation unit for evaluating a quality factor for each of the generated plurality of two-dimensional slices by comparing each of the slices with the anatomical features expected for the respective two-dimensional standard view.

RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.14/781,059, filed on Sep. 29, 2015, which is the U.S. National PhaseApplication under 35 U.S.C. § 371 of International Application No.PCT/IB2014/060004, filed on Mar. 20, 2014, which claims the benefit ofU.S. Provisional Application No. 61/807,885, filed on Apr. 3, 2013, thedisclosure of which is hereby incorporated by reference herein.

FIELD OF THE INVENTION

The present invention relates to three-dimensional ultrasound imaging.In particular, the present invention relates to the generation andevaluation of two-dimensional standard views from three-dimensionalultrasonic volume data. An exemplary technical application of thepresent invention is the generation of two-dimensional transesophagealechocardiography (TEE) images based on one or more obtainedthree-dimensional TEE scans.

BACKGROUND OF THE INVENTION

A transesophageal echocardiogram is an alternative way to perform anechocardiogram. A specialized probe containing an ultrasound transducerat its tip is passed into the patient's esophagus. This allows to recordprecise ultrasound images of different components of the human heart.

For a full transesophageal echocardiography (TEE) examination 20different 2D TEE views have to be acquired. These 2D TEE views arepredefined views (e.g. ME four chamber, ME two chamber, TG basal SAX, .. . ), which are in practice also referred to as the 2D TEE standardviews. In order to acquire these images, the sonographer has toreposition and reorient the ultrasound probe relative to the patientaccording to a very elaborated protocol for each of the 20 2D TEEstandard views. This is a tedious and long procedure, which may takeabout 20 to 30 minutes.

The whole TEE procedure is quite uncomfortable for the patient. Apartfrom that, manually finding the above-mentioned standard views in orderto allow a reliable diagnosis requires a relatively high level of skillof the sonographer (e.g. doctor). Moreover, this process is relativelyerror-prone.

US 2011/0201935 A1, a former patent application filed by the applicant,proposes for the similar field of fetal heart examinations the usage of3D ultrasound scanning technology. The therein proposed ultrasoundimaging system comprises an ultrasound scanning assembly that providesvolume data resulting from a three-dimensional scan of a body. Itfurther comprises a feature extractor that searches for a best matchbetween the volume data and a geometrical model of an anatomical entity.The geometrical model comprises respective segments representingrespective anatomic features. Accordingly, the feature extractorprovides an anatomy-related description of the volume data, whichidentifies respective geometrical locations of respective anatomicfeatures in the volume data. Standard views may therefore beautomatically obtained from the volume data, which is of course lessoperator-dependent and allows a more reliable diagnosis. Compared tomanually acquiring each 2D standard view separately, this is of majoradvantage.

However, there is still need for further improvement.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide an improvedultrasound imaging system, which allows a quicker, more comfortable andmore reliable analysis of an anatomical object, e.g. of the human heart.It is furthermore an object of the present invention to provide acorresponding method and a computer program for implementing suchmethod.

In a first aspect of the present invention an ultrasound imaging systemis presented that comprises:

an image processor configured to receive at least one set of volume dataresulting from a three-dimensional ultrasound scan of a body and toprovide corresponding display data,

an anatomy detector configured to detect a position and orientation ofan anatomical object of interest within the at least one set of volume,

a slice generator for generating a plurality of two-dimensional slicesfrom the at least one set of volume data, wherein said slice generatoris configured to define respective slice locations based on the resultsof the anatomy detector for the anatomical object of interest so as toobtain a set of two-dimensional standard views of the anatomical objectof interest, wherein the slice generator is further configured to definefor each two-dimensional standard view which anatomical features of theanatomical object of interest are expected to be contained within saidtwo-dimensional view, and

an evaluation unit for evaluating a quality factor for each of thegenerated plurality of two-dimensional slices by comparing each of theslices with the anatomical features expected for the respectivetwo-dimensional standard view.

In a further aspect of the present invention a method of generating andevaluating two-dimensional standard views from three-dimensionalultrasonic volume data is presented which comprises the steps of:

receiving at least one set of volume data resulting from athree-dimensional ultrasound scan of a body,

detecting a position and orientation of an anatomical object of interestwithin the at least one set of volume data,

generating a plurality of two-dimensional slices from the at least oneset of volume data, by defining respective slice locations based on thedetected position and orientation of the anatomical object of interestso as to obtain a set of two-dimensional standard views of theanatomical object of interest,

defining for each two-dimensional standard view which anatomicalfeatures of the anatomical object of interest are expected to becontained, and

evaluating a quality factor for each of the generated plurality oftwo-dimensional slices by comparing each of the slices with theanatomical features expected for the respective two-dimensional standardview.

In a still further aspect of the present invention a computer program ispresented comprising program code means for causing a computer to carryout the steps of the above-mentioned method when said computer programis carried out on the computer.

In addition to the method disclosed in US 2011/0201935 A1 it is definedfor each 2D standard view which anatomical features of the anatomicalobject of interest are expected to be contained. An evaluation unit maythen evaluate a quality factor for each of the generated plurality of 2Dslices by comparing each of the slices with the anatomical featuresexpected for the respective 2D standard view.

In other words, for each generated two-dimensional slice (2D standardview) it is computed how good the 2D standard view is covered within thereceived set of 3D ultrasound volume data. Depending on the field ofview of the performed 3D ultrasound scan it may, for example, be thecase that a received set of 3D ultrasound volume data is useful togenerate one or a plurality of 2D standard views, while it is lessuseful to generate other standard views.

Depending on the field of view a received 3D ultrasound volume data setmay, for example, cover most or all parts of the left ventricle of thehuman heart, while it does not cover or only covers few parts of theright ventricle of the human heart. In this case the presentedultrasound imaging system would automatically identify that the receivedvolume data set is only useful for the 2D standard views of the leftventricle, but less useful for the 2D standard views of the rightventricle.

The evaluated quality factor for each of the generated 2D slices maye.g. be a numerical value that results from the comparison of each ofthe generated slices with the anatomical features expected for therespective 2D standard view. For example, the coverage of a 2D standardview by the received set of 3D volume data may be determined bydetermining the overlap of the structures that should be covered(expected anatomical features) and the field of view of the performed 3Dultrasound scan.

According to an embodiment of the present invention, the anatomydetector is configured to conduct a model-based segmentation of the atleast one set of volume data by finding a best match between the atleast one set of volume data and a geometrical model of the anatomicalobject of interest in order to detect the position and orientation ofthe anatomical object of interest. The slice generator may be configuredto define the respective slice locations of the anatomical object ofinterest based on said geometrical model.

In this case a geometrical mesh model of an anatomical object ofinterest (e.g. of the heart) may be used for a model-based segmentationof the 3D ultrasound image (also referred to as volume data). Theplurality of 2D slices may be generated based on said geometrical meshmodel so as to automatically obtain a set of 2D standard views of theanatomical object of interest.

In order to compute the 2D standard views based on the geometricalmodel, landmarks may be encoded in the model. These landmarks encoded inthe geometrical model may be identified and mapped onto the 3Dultrasonic volume data. For example, a set of three or more landmarkscan represent a plane that leads to or corresponds to a 2D standardview. For example to compute the four chamber view of the heart, thisplane is given by the center of the mitral valve, the center of thetricuspid valve and the apex.

It shall be noted that, instead of using a model-based segmentation, theposition and orientation of the anatomical object of interest may alsobe determined (directly) by identifying landmarks or specific anatomicalfeatures within the 3D ultrasound image.

According to a further embodiment of the present invention, the qualityfactor that is evaluated within the evaluation unit for each of thegenerated plurality of two-dimensional slices is a quantitative factorthat includes a ratio to which extent the expected anatomical featuresare included in the respective two-dimensional slice.

According to a further refinement, the evaluation unit is configured toevaluate the quality factor for each of the generated plurality oftwo-dimensional slices by comparing a field of view of each of thetwo-dimensional slices to the geometrical model of the anatomicalobject.

According to a still further embodiment of the present invention, theultrasound imaging system further comprises a display, wherein the imageprocessor is configured to generate display data for simultaneouslyillustrating graphical representations of a plurality of two-dimensionalslices corresponding to different standard views of the anatomicalobject of interest on the display.

In other words, the generated 2D slices may be simultaneously presentedon the display. This allows a doctor an easy comparison of the differentstandard views.

Preferably, the image processor is furthermore configured to generatedisplay data for illustrating a graphical representation of the qualityfactor for each of the two-dimensional slices on the display. Thegraphical representation of the quality factor preferably comprises anicon and/or a percentage. The quality factor may, for example, bepresented as a traffic light to the user. In this case a green lighte.g. shows a good/sufficient coverage of the respective 2D standard viewby the 2D slice generated from the 3D ultrasound volume data. A yellowlight e.g. shows a coverage of the respective 2D standard view by thegenerated 2D slice that could still be sufficient. And a red light e.g.indicates that the field of view of the generated 2D slice does notcover enough anatomical features that should be included in therespective 2D standard view. In this case the user receives a very easyindication about the quality of the computed 2D slices.

According to an embodiment of the present invention, the ultrasoundimaging system further comprises:

a memory for storing a plurality of sets of volume data resulting from aplurality of different three-dimensional scans of a body and for storingthe plurality of two-dimensional slices generated from the plurality ofsets of volume data and their quality factors; and

a selector for selecting for each two-dimensional standard view atwo-dimensional slice having the highest quality factor by comparing theevaluated quality factors of corresponding two-dimensional slicesgenerated from each of the plurality of sets of volume data.

This embodiment leads to a further significant improvement. It allows tocompare 2D slices with each other that correspond to the same 2Dstandard views but were generated from different 3D ultrasound scans(different sets of volume data). The different 3D ultrasound scans maye.g. result from scans at different positions or orientations of theultrasound probe. The ultrasound imaging system may, for example,comprise an initialization unit that initializes the acquisition of a 3Dultrasound scan and the above-mentioned subsequent procedure ofgenerating the 2D slices therefrom each time the position or orientationof the ultrasound probe is changed.

In this case several sets of volume data and 2D slices generatedtherefrom may be stored within a memory. The selector may then selectfor each of the 2D standard views the 2D slice having the highestquality factor. This means that if more than one 3D ultrasound scan isperformed, the system itself automatically selects the best version outof all generated 2D slices for each 2D standard view. Only these bestversions may then be illustrated on the display for each 2D standardview. Thus, only the best examples are illustrated to the user. Incombination with the above-mentioned representation of the qualityfactor on the display (e.g. using an icon such as a traffic light), theuser therefore receives a direct feedback, whether all standard viewsare covered by the combination of all performed 3D ultrasound scans, orwhether he/she has to acquire a further set of 3D volume data byperforming an additional ultrasound scan.

However, it has been shown that a lot less scans have to be performed incontrast to manually acquiring the 2D standard views with a 2Dultrasound scanner. Two or three 3D ultrasound scans of the human heartmay, for example, already be enough in order to generate all 20 2D TEEstandard views. Since the system itself selects the best generated 2Dslice for each 2D standard view, the operation of the presented systemis fairly easy. The user so to say only has to acquire enough 3Dultrasound scans until a “green light” is received for each standardview. This may even be done by the user in a trial and error mannerwithout having to follow the usual elaborated protocols for acquiringthe predefined standard views.

Even though in the foregoing paragraphs it has been mainly focused onthe generation of transesophageal echocardiography (TEE), it shall bepointed out that the presented ultrasound imaging system may also beused for generating and evaluating 2D standard views of other organs orother anatomical objects of humans and/or animals. It could be used in asimilar way e.g. for an analysis of the liver or an unborn baby (fetalultrasound).

In the foregoing it has mainly been focused on the image processing partof the presented ultrasound imaging system. According to a furtherembodiment, the ultrasound imaging system may further include:

a transducer array configured to provide an ultrasound receive signal,

a beam former configured to control the transducer array to perform thethree-dimensional scan of the body, and further configured to receivethe ultrasound receive signal and to provide an image signal,

a controller for controlling the beam former, and

a signal processor configured to receive the image signal and to providethe three-dimensional volume data.

According to a further preferred embodiment, said controller may beconfigured to control the beam former to control the transducer array toperform an additional two-dimensional scan for a two-dimensionalstandard view of the anatomical object of interest if the quality factorof one of the plurality of two-dimensional slices generated by the slicegenerator is above a predetermined threshold.

In other words, this means that the ultrasound imaging system isconfigured to automatically perform an additional 2D ultrasound scan ifit is found in the above-mentioned analysis that one of the slicesgenerated from the 3D ultrasound volume data covers the respective 2Dstandard view in a sufficiently good manner. The system would thenrecognize that the acquired field of view at the position andorientation of the ultrasound probe is meaningful for acquiring the 2Dstandard view in a direct manner (by an extra 2D ultrasound scan at thisposition and orientation). This additional 2D scan would then be takenin the further image processing as 2D standard view instead ofgenerating said 2D standard view by an interpolation from the 3D volumedata as mentioned above. In this case the local image resolution mayeven be increased for said standard view.

It shall be understood that the claimed method has similar and/oridentical preferred embodiments as the claimed ultrasound imagingsystem, as defined above and as defined in the dependent claims.

According to an embodiment, the position and orientation of theanatomical object of interest are detected by conducting a model-basedsegmentation of the at least one set of volume data and finding a bestmatch between the at least one set of volume data and a geometricalmodel of the anatomical object of interest, and wherein the respectiveslice locations are defined based on said geometrical model.

According to a further embodiment, the claimed method comprises thesteps of:

receiving and storing a plurality of sets of volume data resulting froma plurality of three-dimensional scans of a body,

generating and storing a plurality of different two-dimensional slicesgenerated from each of the plurality of sets of volume data togetherwith their quality factors; and

selecting for each two-dimensional standard view a two-dimensional slicehaving the highest quality factor by comparing the evaluated qualityfactors of corresponding two-dimensional slices generated from each ofthe plurality of sets of volume data.

According to a further embodiment, the claimed method comprises thesteps of simultaneously illustrating graphical representations of aplurality of two-dimensional slices corresponding to different standardviews of the anatomical object of interest on a display.

According to a further embodiment, the claimed method comprises the stepof illustrating a graphical representation of the quality factor foreach of the two-dimensional slices on a display.

According to a still further embodiment, the claimed method comprisesthe step of performing an additional two-dimensional scan for atwo-dimensional standard view of the anatomical object of interest ifthe quality factor of one of the generated plurality of two-dimensionalslices is above a predetermined threshold.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other aspects of the invention will be apparent from andelucidated with reference to the embodiment(s) described hereinafter. Inthe following drawings

FIG. 1 shows a schematic representation of an ultrasound imaging systemin use to scan a volume of a patient's body;

FIG. 2 shows a schematic block diagram of an embodiment of theultrasound imaging system;

FIG. 3 schematically shows an overview of different 2D standard views ofa transesophageal echography (TEE);

FIG. 4 shows a flow diagram to illustrate an embodiment of the methodaccording to the present invention;

FIG. 5 shows a first exemplary illustration of results received with theultrasound imaging system;

FIG. 6 shows a second exemplary illustration of results received withthe ultrasound imaging system; and

FIG. 7 shows a third exemplary illustration of results received with theultrasound imaging system.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1 shows a schematic illustration of an ultrasound system 10according to an embodiment, in particular a medical three-dimensional(3D) ultrasound imaging system. The ultrasound imaging system 10 isapplied to inspect a volume of an anatomical site, in particular ananatomical site of a patient 12. The ultrasound system comprises anultrasound probe 14 having at least one transducer array having amultitude of transducer elements for transmitting and/or receivingultrasound waves. In one example, the transducer elements each cantransmit ultrasound waves in form of at least one transmit impulse of aspecific pulse duration, in particular a plurality of subsequenttransmit pulses. The transducer elements are preferably arranged in atwo-dimensional array, in particular for providing a multi-planar orthree-dimensional image.

A particular example for a three-dimensional ultrasound system which maybe applied for the current invention is the CX40 Compact Xtremeultrasound system sold by the applicant, in particular together with aX6-1 or X7-2t TEE transducer of the applicant or another transducerusing the xMatrix technology of the applicant. In general, matrixtransducer systems as found on Philips iE33 systems or mechanical 3D/4Dtransducer technology as found, for example, on the Philips iU22 andHD15 systems may be applied for the current invention.

A 3D ultrasound scan typically involves emitting ultrasound waves thatilluminate a particular volume within a body, which may be designated astarget volume. This can be achieved by emitting ultrasound waves atmultiple different angles. A set of volume data is then obtained byreceiving and processing reflected waves. The set of volume data is arepresentation of the target volume within the body.

It shall be understood that the ultrasound probe 14 may either be usedin a non-invasive manner (as shown in FIG. 1) or in an invasive manneras this is usually done in TEE (not explicitly shown). The ultrasoundprobe 14 may be hand-held by the user of the system, for example medicalstaff or a doctor. The ultrasound probe 14 is applied to the body of thepatient 12 so that an image of an anatomical site, in particular ananatomical object of the patient 12 is provided.

Further, the ultrasound system 10 may comprise a controlling unit 16that controls the provision of a 3D image via the ultrasound system 10.As will be explained in further detail below, the controlling unit 16controls not only the acquisition of data via the transducer array ofthe ultrasound probe 14, but also signal and image processing that formthe 3D images out of the echoes of the ultrasound beams received by thetransducer array of the ultrasound probe 14.

The ultrasound system 10 may further comprise a display 18 fordisplaying the 3D images to the user. Still further, an input device 20may be provided that may comprise keys or a keyboard 22 and furtherinputting devices, for example a trackball 24. The input device 20 mightbe connected to the display 18 or directly to the controlling unit 16.

FIG. 2 shows a schematic block diagram of the ultrasound system 10. Asalready laid out above, the ultrasound system 10 comprises an ultrasoundprobe (PR) 14, the controlling unit (CU) 16, the display (DI) 18 and theinput device (ID) 20. As further laid out above, the probe (PR) 14comprises a phased two-dimensional transducer array (TR) 26. In general,the controlling unit (CU) 16 may comprise a central processing unit(CPU) 28 that may include analog and/or digital electronic circuits, aprocessor, microprocessor or the like to coordinate the whole imageacquisition and provision. However, it has to be understood that thecentral processing unit (CPU) 28 does not need to be a separate entityor unit within the ultrasound system 10. It can be a part of thecontrolling unit 16 and generally be hardware or software implemented.The current distinction is made for illustrative purposes only. Thecentral processing unit (CPU) 28 as a part of the controlling unit (CU)16 may control a beam former (BF) 30 and, by this, what images of thevolume 40 are taken and how these images are taken. The beam former (BF)30 generates the voltages that drive the transducer array (TR) 26,determines repetition frequencies, it may scan, focus and apodize thetransmitted beam and the reception of receive beam(s) and may furtheramplify filter and digitize the echo voltage stream returned by thetransducer array (TR) 26. Further, the central processing unit (CPU) 28of the controlling unit (CU) 16 may determine general scanningstrategies. Such general strategies may include a desired volumeacquisition rate, lateral extent of the volume, an elevation extent ofthe volume, maximum and minimum line densities and scanning line times.The beam former (BF) 30 further receives the ultrasound signals from thetransducer array (TR) 26 and forwards them as image signals.

Further, the ultrasound system 10 comprises a signal processor (SP) 32that receives the image signals. The signal processor (SP) 32 isgenerally provided for analog-to-digital-converting, digital filtering,for example, bandpass filtering, as well as the detection andcompression, for example a dynamic range reduction, of the receivedultrasound echoes or image signals. The signal processor 32 forwardsimage data.

Further, the ultrasound system 10 comprises an image processor (IP) 34that converts image data received from the signal processor 32 intodisplay data. In particular, the image processor 34 receives the imagedata, preprocesses the image data and may store it in a memory (MEM) 36.This image data is then further post-processed to provide images to theuser via the display 18. In the current case, in particular, the imageprocessor 34 may form the three-dimensional images out of a multitude oftwo-dimensional images.

The ultrasound system 10 may in the current case further comprise ananatomy detector (AD) 38, a slice generator (SLG) 40 and an evaluationunit (EU) 42. It shall be noted that the latter mentioned components mayeither be realized as separate entities, but may also be included in theimage processor 34. All these components may be hardware and/or softwareimplemented.

The anatomy detector (AD) 38 identifies the orientation and position ofthe anatomical object of interest within the acquired 3D volume data.The anatomy detector (AD) may thereto be configured to conduct amodel-based segmentation of the acquired 3D volume data. This may bedone by finding a best match between the at least one set of volume dataand a geometrical mesh model of the anatomical object of interest. Themodel-based segmentation may, for example, be conducted in a similarmanner as this is described for a model-based segmentation of CT imagesin Ecabert, O. et al.: “Automatic Model-based Segmentation of the Heartin CT Images”, IEEE Transactions on Medical Imaging, Vol. 27(9), p.1189-1291, 2008. The geometrical mesh model of the anatomical object ofinterest may comprise respective segments representing respectiveanatomic features. Accordingly, the anatomy detector 38 may provide ananatomy-related description of the volume data, which identifiesrespective geometrical locations of respective anatomic features in thevolume data.

Such a model-based segmentation usually starts with the identificationof the orientation of the anatomical object of interest (e.g. the heart)within the 3D ultrasonic volume data. This may, for example, be doneusing a three-dimensional implementation of the Generalized HoughTransform. Pose misalignment may be corrected by matching thegeometrical model to the image making use of a global similaritytransformation. The segmentation comprises an initial model that roughlyrepresents the shape of the anatomical object of interest. Said modelmay be a multi-compartment mesh model. This initial model will bedeformed by a transformation. This transformation is decomposed into twotransformations of different kinds: A global transformation that cantranslate, rotate or rescale the initial shape of the geometrical model,if needed, and a local deformation that will actually deform thegeometrical model so that it matches more precisely to the anatomicalobject of interest. This is usually done by defining the normal vectorsof the surface of the geometrical model to match the image gradient;that is to say, the segmentation will look in the received ultrasonicimage for bright-to-dark edges (or dark-to-bright), which usuallyrepresent the tissue borders in ultrasound images, i.e. the boundariesof the anatomical object of interest.

The segmented 3D volume data may then be further post-processed. Theslice generator (SLG) 40 generates a plurality of two-dimensional slicesfrom the 3D volume data. Landmarks are thereto encoded within thegeometrical model that defines the planes of said 2D slices. A set ofthree or more landmarks can represent a plane. These encoded landmarksmay be mapped onto the segmented 3D volume data so as to obtain a set of2D standard views of the anatomical object of interest generated fromthe 3D volume data. The slice generator 40 may be furthermore configuredto define for each 2D standard view which anatomical features of theanatomical object of interest are expected to be contained within saidview. This may be done using the geometrical model that is encoded withthe anatomic features of the anatomical object of interest. It shouldthus be known which anatomical features should occur in which 2Dstandard view.

The evaluation unit (EU) 42 may then evaluate a quality factor for eachof the generated plurality of 2D slices by comparing each of saidgenerated slices with the anatomical features expected for therespective 2D standard view. In other words, the evaluation unit 42computes the coverage of each of the 2D standard views by the 3D volumedata. This may be done by computing the overlap of the structure thatshould be covered and the field of view of the 3D ultrasound scan. Thequality factor that is evaluated within the evaluation unit 42 for eachof the generated plurality of 2D slices may thus be a quantitativefactor that includes a ratio to which extent the expected anatomicalfeatures are included in the respective 2D slice. This may be done bycomparing the field of view of each of the 2D slices to the geometricalmodel of the anatomical object.

In still other words, this means that for each 2D slice that isgenerated from the received 3D ultrasound volume data, it is determinedhow good the 2D standard view, that corresponds to the generated 2Dslice, is covered. This information can be presented as a graphicalicon, e.g. as a traffic light, and/or as a percentage on the display 18.

As it will be explained further below in detail with reference to FIGS.5 to 7, the generated 2D slices of the anatomical object of interest arepreferably illustrated on the display 18 simultaneously, wherein eachillustrated 2D slice is illustrated together with a graphicalrepresentation of the quality factor (icon and/or percentage) thatindicates the quality of the respective 2D slice.

In practice there is usually not only performed a single 3D ultrasoundscan of the anatomical object of interest. Preferably, a plurality of 3Dultrasound scans of the anatomical object of interest are performed.This results in a plurality of sets of volume data, which result fromthe plurality of different 3D scans of the body. For each of these setsof 3D volume data, the above-mentioned processing (segmentation, slicegeneration and evaluation) is performed by the ultrasound system 10. Theplurality of sets of volume data resulting from the different 3D scansand the 2D slices that are generated in the above-mentioned way fromsaid sets of volume data may be stored within the memory (MEM) 36together with the evaluated quality factors of each of the 2D slices.

In this case a selector (SEL) 44 is configured to select for each 2Dstandard view a 2D slice that has the highest quality factor. This maybe done by comparing the evaluated quality factors of corresponding 2Dslices that are generated from each of the plurality of 3D sets ofvolume data which are stored in the memory 36. In other words, theselector 44 selects for each standard view the best 2D slice out of all2D slices that have been generated from the different sets of 3D volumedata (different ultrasound scans). This means that the different 2Dstandard views that are simultaneously illustrated on the display 18 mayresult from different 3D ultrasound scans, wherein the selector 44automatically determines from which 3D volume data set a specific 2Dstandard view may be generated best.

This will be explained in the following in further detail by example ofa transesophageal echocardiography (TEE).

For a full TEE examination, 20 different 2D TEE standard views have tobe acquired. An overview of the different standard views is given inschematical manner in FIG. 3. FIG. 3a e.g. illustrates the ME fourchamber view, FIG. 3b the ME two chamber view, FIG. 3c the ME LAX viewand so on.

FIG. 4 shows a schematic block diagram for illustrating the methodaccording to an embodiment of the present invention. In a first step S10a set of volume data resulting from a 3D ultrasound scan of a body isreceived. In the following step S12 a position and orientation of ananatomical object of interest (e.g. the human heart) is detected withinthe at least one set of volume data. Thereto, a model-based segmentationof the at least one set of volume data may be conducted. As alreadymentioned above, this is done by finding a best match between the atleast one set of volume data and a geometrical model of the human heart.

Then, said model is used to compute the planes of all 20 TEE standardviews. This is done in step S14 by generating a plurality of 2D slicesfrom the at least one set of 3D volume data. Thereto, the respectiveslice locations are defined based on the geometrical model of the heart.Due to the segmentation that has been performed in advance (in stepS12), these respective slice locations may be mapped onto the 3D volumedata, such that it is possible to compute the 2D slices from the 3Dvolume data set by interpolating the 3D image. For example to computethe ME four chamber view (see FIG. 3a ), the plane is given by thecenter of the mitral valve, the center of the tricuspid valve and theapex.

Then, in step S16 it is defined for each 2D standard view whichanatomical features of the heart are expected to be contained in saidstandard view. This may be done by encoding the geometrical model withan anatomy-related description that identifies segments of the heartwithin each 2D standard view that correspond to respective anatomicfeatures, for example, the heart chambers, the main vessels, the septa,the heart valves, etc. If the geometrical model is encoded with thisanatomy-related information, it is easier in the further procedure toevaluate whether the generated 2D slices cover all information thatshould be included within the respective 2D standard view.

In step S18 it is then evaluated for each of the generated 2D slices howgood the 2D standard view is covered. Thereto, a quality factor iscomputed for each of the generated 2D slices, wherein said qualityfactor may be a quantitative factor that includes a ratio to whichextent the expected anatomical features are included in the respective2D slice. This may be done by comparing the field of view of each of thegenerated 2D slices to the geometrical model of the heart.

FIG. 5 shows six 2D slices that have been generated in theabove-mentioned way based on a single 3D TEE image (herein referred toas a single set of volume data). The results of the performedsegmentation are therein illustrated by border lines 46. FIG. 5a showsthe 2D slice that corresponds to the ME four chamber standard view(compare to FIG. 3a ). FIG. 5B therein shows the 2D slice thatcorresponds to the ME two chamber standard view (compare to FIG. 3b ).FIG. 3d shows the generated 2D slice that corresponds to the TE mid SAXstandard view (compare to FIG. 3d ). FIG. 5h shows the generated 2Dslice that corresponds to the ME AV SAX standard view (compare to FIG.3h ). FIG. 5i shows the generated 2D slice that corresponds to the ME AVLAX standard view (compare to FIG. 3i ). And FIG. 5m shows the generated2D slice that corresponds to the ME RV inflow-outflow standard view(compare to FIG. 3m ).

As it may be seen, most of the anatomical features of interest arewithin the slices 5 a, b and d, i.e. most of the border lines 46 arewithin the field of view. The quality factors that have been evaluatedfor these slices are therefore comparatively high, which is indicated inFIGS. 5a, b and d by means of a graphical icon 48 that is illustrated inthe upper right corner of each slice image and represents a schematicaltraffic light showing a green light.

It may be furthermore seen that the generated slices 5 h and i are stillacceptable, because the main anatomical features of interest, e.g. theaortic valve within FIG. 5h , is still within the field of view. Thetraffic light 48′ therefore shows a yellow light for these slices. InFIG. 5m most of the border lines 46 are however out of the field ofview, meaning that the anatomical features of interest, i.e. the in andoutflow of the right ventricle, are not fully covered. The quality ofthis generated 2D slice is thus evaluated to be rather low, which isindicated in FIG. 5m with a traffic light 48″ that shows a red light.

Returning back to FIG. 4 now, the method steps S10-S18 are repeated forevery new 3D TEE image. This means that for every 3D TEE image (every 3Dvolume data set), all 20 2D slices are generated and evaluated thatcorrespond to the 20 different 2D TEE standard views illustrated in FIG.3. For every 2D slice it is defined, which anatomical features are to beexpected therein, i.e. which border lines 46 should occur in these 2Dslices (step S16). And for every 2D slice it is evaluated, whether theexpected border lines are within the field of view, or to which extendthis is the case (step S18).

FIG. 6 illustrates 2D slices that have been generated (and evaluated)based on a second 3D TEE image (second set of volume data) with adifferent field of view. From FIG. 6 it may be seen that the generatedslices 6 a, b and d are compared to the slices shown in FIGS. 5a, b andd rather unsuitable (indicated by red traffic light 48″). However, thegenerated 2D slices corresponding to the ME AV SAX standard view (FIG.6h ), the ME AV LAX standard view (FIG. 6i ) and to the ME RVinflow-outflow standard view (see FIG. 6m ) have a rather good quality,since the anatomical features of interest (border lines 46) are thistime within the field of view.

It may therefore be seen that the 2D standard views a, b and d are bestcovered within the 2D slices that were generated from the first 3Dvolume data set (illustrated in FIG. 5 a, b and d), while the 2Dstandard views h, i and m are best covered within the 2D slices thatwere generated from the second 3D volume data set (illustrated in FIGS.6h, i and m ).

In step S20 (see FIG. 4) the best version for each 2D standard view isthen automatically selected. For each 2D standard view one generated 2Dslice is selected that has the highest quality factor. This may be doneby comparing the evaluated quality factors of corresponding 2D slicesgenerated from each of the received sets of volume data (from each ofthe received 3D TEE images). This “best selection” is finallyillustrated on the display in step S24.

The result is shown in FIG. 7. As it may be seen in FIG. 7, the system10 automatically selected the more suitable 2D slices that weregenerated from the first 3D TEE image as 2D standard views a, b and d,while it automatically selected the 2D slices that were generated fromthe second 3D TEE image as 2D standard views h, i and m. In summary,this means that only two 3D TEE images were necessary in this example togenerate the exemplarily shown six 2D standard views, whereas sixdifferent ultrasound scans would be required when manually scanning thepatient with a regular 2D ultrasound scanning system. The furthersignificant advantage is that the system selects the best 2D slices byitself. The presented method is thus less error-prone and fastercompared to the conventional TEE procedure.

A still further improvement of the method schematically illustrated inFIG. 4 is shown by step S22. Instead of using the 2D slices that wereinterpolated from the 3D volume data set, the 2D slices may also begenerated by performing an additional 2D scan as soon as the systemrecognizes that a quality factor of a 2D slice that is generated insteps S10-S18 is above a predetermined threshold value. This means thatas soon as the system recognizes that the field of view of the taken 3Dimage is suitable for a specific 2D standard view, the imagingparameters for this 2D standard view from the current location of thetransducer probe 14 are computed and the transducer probe 14automatically performs an additional 2D scan to directly receive the 2Dstandard view. This “extra” acquisition should however only be done ifit has been found in step S18 that the quality of the generated 2D sliceis rather high, meaning that the position and orientation of thetransducer probe 14 is suitable for acquiring the respective 2D standardview.

It shall be noted that step S22 is not a mandatory, but an optionalmethod step. Of course, a combination of both, generating the 2D slicesfrom the 3D volume data set and generating the 2D slices directly byperforming an additional 2D scan, is possible as well.

While the invention has been illustrated and described in detail in thedrawings and foregoing description, such illustration and descriptionare to be considered illustrative or exemplary and not restrictive; theinvention is not limited to the disclosed embodiments. Other variationsto the disclosed embodiments can be understood and effected by thoseskilled in the art in practicing the claimed invention, from a study ofthe drawings, the disclosure, and the appended claims.

In the claims, the word “comprising” does not exclude other elements orsteps, and the indefinite article “a” or “an” does not exclude aplurality. A single element or other unit may fulfill the functions ofseveral items recited in the claims. The mere fact that certain measuresare recited in mutually different dependent claims does not indicatethat a combination of these measures cannot be used to advantage.

A computer program may be stored/distributed on a suitable medium, suchas an optical storage medium or a solid-state medium supplied togetherwith or as part of other hardware, but may also be distributed in otherforms, such as via the Internet or other wired or wirelesstelecommunication systems.

Any reference signs in the claims should not be construed as limitingthe scope.

1. An ultrasound imaging system comprising: an image processorconfigured to receive at least one set of volume data resulting from athree-dimensional ultrasound scan of a body and to provide correspondingdisplay data, an anatomy detector configured to detect a position andorientation of an anatomical object of interest within the at least oneset of volume data, a slice generator for generating a plurality oftwo-dimensional slices from the at least one set of volume data, whereinsaid slice generator is configured to define respective slice locationsbased on the results of the anatomy detector for the anatomical objectof interest so as to obtain a set of two-dimensional standard views ofthe anatomical object of interest, wherein the slice generator isfurther configured to define for each two-dimensional standard viewwhich anatomical features of the anatomical object of interest areexpected to be contained, and an evaluation unit for evaluating aquality factor for each of the generated plurality of two-dimensionalslices by comparing each of the slices with the anatomical featuresexpected for the respective two-dimensional standard view.
 2. Theultrasound imaging system of claim 1, wherein the anatomy detector isconfigured to conduct a model-based segmentation of the at least one setof volume data by finding a best match between the at least one set ofvolume data and a geometrical model of the anatomical object of interestin order to detect the position and orientation of the anatomical objectof interest, and wherein the slice generator is configured to define therespective slice locations of the anatomical object of interest based onsaid geometrical model.
 3. The ultrasound imaging system of claim 1,further comprising: a memory for storing a plurality of sets of volumedata resulting from a plurality of different three-dimensional scans ofa body and for storing the plurality of two-dimensional slices generatedfrom the plurality of sets of volume data and their quality factors; anda selector for selecting for each two-dimensional standard view atwo-dimensional slice having the highest quality factor by comparing theevaluated quality factors of corresponding two-dimensional slicesgenerated from each of the plurality of sets of volume data.
 4. Theultrasound imaging system of claim 1, wherein the quality factor that isevaluated within the evaluation unit for each of the generated pluralityof two-dimensional slices is a quantitative factor that includes a ratioto which extend the expected anatomical features are included in therespective two-dimensional slice.
 5. The ultrasound imaging system ofclaim 2, wherein the evaluation unit is configured to evaluate thequality factor for each of the generated plurality of two-dimensionalslices by comparing a field of view of each of the two-dimensionalslices to the geometrical model of the anatomical object.
 6. Theultrasound imaging system of claim 1, further comprising a display,wherein the image processor is configured to generate display data forsimultaneously illustrating graphical representations of a plurality oftwo-dimensional slices corresponding to different standard views of theanatomical object of interest on the display.
 7. The ultrasound imagingsystem of claim 6, wherein the image processor is furthermore configuredto generate display data for illustrating a graphical representation ofthe quality factor for each of the two-dimensional slices on thedisplay.
 8. The ultrasound imaging system of claim 7, wherein thegraphical representation of the quality factor comprises an icon and/ora percentage.
 9. The ultrasound imaging system of claim 1, furthercomprising: a transducer array configured to provide an ultrasoundreceive signal, a beam former configured to control the transducer arrayto perform the three-dimensional scan of the body, and furtherconfigured to receive the ultrasound receive signal and to provide animage signal, a controller for controlling the beam former, and a signalprocessor configured to receive the image signal and to provide thethree-dimensional volume data.
 10. The ultrasound imaging system ofclaim 9, wherein the controller is configured to control the beam formerto control the transducer array to perform an additional two-dimensionalscan for a two-dimensional standard view of the anatomical object ofinterest if the quality factor of one of the plurality oftwo-dimensional slices generated by the slice generator is above apredetermined threshold.
 11. A method of generating and evaluatingtwo-dimensional standard views from three-dimensional ultrasonic volumedata, the method comprising the steps of: receiving at least one set ofvolume data resulting from a three-dimensional ultrasound scan of abody, detecting a position and orientation of an anatomical object ofinterest within the at least one set of volume data, generating aplurality of two-dimensional slices from the at least one set of volumedata, by defining respective slice locations based on the detectedposition and orientation of the anatomical object of interest so as toobtain a set of two-dimensional standard views of the anatomical objectof interest, defining for each two-dimensional standard view whichanatomical features of the anatomical object of interest are expected tobe contained, and evaluating a quality factor for each of the generatedplurality of two-dimensional slices by comparing each of the slices withthe anatomical features expected for the respective two-dimensionalstandard view.
 12. The method of claim 11, wherein the position andorientation of the anatomical object of interest are detected byconducting a model-based segmentation of the at least one set of volumedata and finding a best match between the at least one set of volumedata and a geometrical model of the anatomical object of interest, andwherein the respective slice locations are defined based on saidgeometrical model.
 13. The method of claim 11, further comprising thesteps of: receiving and storing a plurality of sets of volume dataresulting from a plurality of three-dimensional scans of a body,generating and storing a plurality of different two-dimensional slicesgenerated from each of the plurality of sets of volume data togetherwith their quality factors; and selecting for each two-dimensionalstandard view a two-dimensional slice having the highest quality factorby comparing the evaluated quality factors of correspondingtwo-dimensional slices generated from each of the plurality of sets ofvolume data.
 14. The method of claim 12, wherein the quality factor foreach of the generated plurality of two-dimensional slices is evaluatedby comparing a field of view of each of the two-dimensional slices tothe geometrical model of the anatomical object.
 15. Computer programcomprising program code means for causing a computer to carry out thesteps of the method as claimed in claim 11 when said computer program iscarried out on a computer.